Ok here is the scenario (it has happened a couple of time)
Using the supplied wireless charger and cable, I turn off the S3 and put it on charge and leave it all night. When I come back it is sitting in the mid 70% and deosn't seem to charge any more. I take it off and replace it, only for it to start flashing an exclamation mark in a yellow trianggle (not a good sign if I had left it a long time!).
Lastely I take it off and replace it a third time for it to fully charge to 100% (so it is capable).
What gives? Why did it work the 3rd time? Wht's with the warning sign, it didn't seem overly hot. (hopefully not Note7 battery syndrom!)
